66

I'm a programmer and private pilot, so maybe I can help dispel some of those fears. The computers that run a commercial airplane are conceptually much simpler than the one that runs your phone. This means far less chance of a bug in the software, just because there's less for the programmer to keep track of. If your phone restarts, it doesn't imperil ...


48

Congrats on earning your wings! Because ammeters measure the flow of current (positive or negative) they can immediately show when the alternator is no longer providing power and the battery is discharging instead. In a voltmeter, like most modern automobiles have, you would have to wait to see the charge level on the battery drop, and by that point, several ...


33

It's the second option. In any other context, a small aircraft's electrical system would be called "24V". But the alternator regularly puts out 28V, so that's what's typically expected if you hook up your multimeter while the engine's running. Of course, the on-board equipment can operate over a wide range of voltages, often down to as little as 20V.


25

Multiple sources indicate that the 28 VDC bus on aircraft powered by 24 VDC batteries, and the 24 VDC systems on truck powered by 28 VDC alternators, are basically the same thing, and that is is just a naming convention. The number of cells is a function of the nominal voltage and the cell type. From this site: Lead Acid: 2 volts/cell Nickel based for ...


25

Before we start, it's important to say that your concern is not irrational. If this were to happen, or if your plane's control systems were to otherwise malfunction in a dangerous manner, your life would genuinely be in danger. You aren't the first person to have thought of this, though. For this reason, we have a category of control systems we describe ...


23

Other than the APU, there are multiple ways to provide electrical power to an aircraft: Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery ...


22

Because it displays how much current, and thus how much power, your electrical system is consuming. This provides a quick reference for diagnosing problems. Negative values can indicate a malfunctioning alternator and large power draws can indicate a short circuit somewhere in the system.


19

The more unpleasant a failure of some system is, the more tools you get to prevent, diagnose and mitigate the failure. An ordinary passenger car can stop in a middle of nowhere because the alternator failed and the battery depleted. Quite unpleasant, but rarely fatal - and modern cars tend to be reliable enough anyway. An offroad rig with winches, extra ...


17

This is somewhat dependent on the aircraft of course, so I will focus on the Boeing 737 NG series as an example of a typical airliner. Details will differ with other aircraft, but the general concept should be the same. When there is loss of thrust on both engines, both engine driven generators will stop providing power. The battery will take over powering ...


16

Let me start of with two facts that pretty much answer your question: A 24V battery is a battery that can output at least 24V over the majority of its capacity. To charge a rechargeable battery you need to push charge into it by providing it with a higher voltage than what the battery is currently at. To put a bit more meat on, here is a typical discharge ...


15

Onboard batteries for DC and a ground power supply for AC. The ground supply can come either from an airport vehicle or from the stand itself. Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or ...


13

Although the accepted answer is basically correct, as an additional backup source of power (for hydraulics or electric, depending on the aircraft), there can be a Ram air turbine (RAT - https://en.wikipedia.org/wiki/Ram_air_turbine) that can be deployed in a failure of both primary and secondary energy sources. It uses the airflow from the airplane's speed ...


10

Your concerns are reasonable and justified. A mid-air shutdown or reboot would be catastrophic to an airliner. Which is why, engineers designed the systems such that this scenario is practically impossible to happen. Electrical power An airliner has multiple electrical power source. Each jet engine has a built-in generator. When the turbine spins, ...


8

This would certainly be possible, but the current status (pun intended) of the battery technology makes it pretty much pointless. The charging would simply take too long: for example, Eviation Alice has a battery capacity of 900kWh. If we were to charge, say, 75% of this (because you would need to have some reserve capacity in case charging does not work ...


8

Actual details vary between aircrafts. But in general, the battery can supply essential systems for some time and then APU/RAT/... should kick in.


7

It's a function of the relative demand each service puts on the APU. You have to remember that bleed is power consumed; you're just taking it in a different form. As a turboshaft jet engine, the primary limitation on total power is the amount of heat the turbine can take. When you take bleed from the compressor, the turbine is forced to generate a lot of ...


7

The reason ammeters were dropped in cars is they were (and are as used in airplanes) wired to the battery and only show the current flow into or out of the battery. The battery's nominal voltage is 12, but the system operating voltage is about 14, and the voltage regulator varies the alternator field to keep roughly 14 volts in the system so that the ...


6

@Jpe61 is correct in his comment that it's likely an electronics issue, since indeed a VSCF is mechanically simpler. VSCF is also used on the MD-90, with poor initial reliability$^1$ – MDC went back to IDGs for the MD-95 (717).$^1$ It's also used on the 777 (only for backup, also with poor initial reliability$^2$), and on the F/A-18.$^3$ Capacitors The F/A-...


6

Not to burst your bubble, but doing this "cheap" isn't possible. First look at range. Light aircraft that have a 2-ton+ payload have limited range, look at the upcoming Cessna 408, it can carry 3 tons but only has a 1,000 mile ferry range. In order to increase the range, you need to carry more fuel, reducing your load. So lets say you dedicated 1 ...


5

Different aircraft and manufacturers take very different approaches. 1. Boeing 777 The B777 has three Primary Flight Computers (PFC) that are responsible for flight control laws computation and four Actuator Control Units (ACE) that are responsible for the closed-loop control of their responsible flight control surfaces. The ACE is primarily an analog ...


5

Tesla now has batteries to the point where you can recoup energy for a 4-hour drive in 30 minutes. That's in full-on production, you can buy it and do it at retail today. The biggest challenge Tesla has is keeping the batteries cool during this slam charging; and in an airplane we have a huge surface area being blown by a slipstream. Have the battery ...


4

What's the plug pair called? I don't think there's an "official" name for it, but it's usually referred to as the "ground power connection" or something similar. Also, there's usually only one connection; only the biggest commercial aircraft need two connections simply because one connection can't supply enough power. What's the ISO/whatever standard ...


4

as somebody who did software tests on an unimportant (class D, will explain soon) system for an airplane to be approved to be landed on civilian airports: In airplane there is a strict hierarchy on what kind of software functions mean; they are listed in DO-178B. Class A systems are assumed to be "failure free"; they are extremely well tested. These ...


4

But in reality, the fully charged/charging/float voltage of the system with alternator running is higher Yes. If a car battery states 12V that's kind-of the lower limit. As in, it really shouldn't drop below 11.8 when fully discharged, although depending on the type of battery and vehicle it may still function (for some values of function). A fully charged ...


4

This question shows the fallacy of electric propulsion in its current state. The electricity needs to be generated using non-environmentally friendly means. Even solar power is unfriendly due to the process for making the current panels. Hydro and geothermal power would not work in this scenario. Even the production and disposal of the batteries have ...


4

Your linked Google Images search leads to examples such as this: Source: amazon.com The manufacturer being Mechanical (the company's name). A little dive into the patents reveals this invention: Source: Google Patents US3145281A Also by Mechanical, for, you guessed it, a Multipole circuit breaker with trip devices located in the housing of a single pole. ...


4

They are both energised all of the time except emergency situations. The essential devices can be switched between them, the non-essential ones will be turned off in such cases. There is actually a couple more buses than two. The main ones, AC BUS 1 and 2¹, are powered by one engine-driven generator each, and are normally not connected. This has some ...


4

There is no shortage of air freight companies that can quickly ship cargo to nearly any airport in the world, and since they have economy of scale and lots of experience dealing with regulators, you will never beat their costs. Africa's main logistics problem is the so-called "last mile": getting supplies from an airport to where they're actually needed. In ...


4

As others have pointed out, the range you're thinking of is unrealistic. There are other problems too: making sure your dropped load doesn't hit anyone and will land in the right spot (and not, for instance in the nearby swamp) is not easy. And in regions remote enough to qualify for this service, you can't count on qualified personnel to be available to ...


4

Yes, in theory, but you would have to do a total energy analysis to decide if it's worth it. On the surface of it, generators consume fuel not being made into thrust. Watts being made to power things is watts not going out the tailpipe. A good example of the potential benefit is the switch to LED cabin lighting. A 40w incandescent light is more or less a ...


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